MakkMarci

iTrader: (1)

Hi!

I bought a Pontiac Firebird Formula 5.7l V8.
the problem:

When I driving with about 25mph, I hear bamm.. bamm.. bammm sound, *about two-three bass sounds/sec..
When I driving with about 85mph, my car vibrating heavily
When I set my automatic transmission to Neutral, no changes, I dont know what happening

I changed these items:
rear carrier
rear shocks
rear tires
rear bushing/front bushing to Energy suspension bushing
when I exchanged rear bushing,the sounds louder
I exchanged ALL rear bearings too...

who can I help me?
Im in europe, and I cant go to the official service

ps: sorry my language

WS6WRX

iTrader: (1)

Driveshaft out of balance? Just a guess.

MakkMarci

iTrader: (1)

Good idea, how can I balance it?

jboomer

or too much angle in your driveline u-joint.

MakkMarci

iTrader: (1)

okey, how can I check it/fix it?

CTSmechanic

iTrader: (2)

I wouldnt worry about driveline angle unless you've done some suspension mods like lowering even then its a strech..check the torque on the pinion nut as well as all the TQ arm bolts.... flip the driveshaft 180 degrees... rotate the tires to see if the problem moves check the driveshaft for dents increased road noise/vibration is pretty common with poly bushings check the u joints for any unusually tight spots or excessive play as well as any ratchety movements if the cars in neutral it shouldnt matter because its still moving the same speed as the pinion..

elderon

I'm guessing driveshaft. Did you swap your gears by chance? I had the stock 2:73 rear end with the steel driveshaft. This works fine unless you upgrade your gears. Once I swapped to a 3:42 I had major vibration issues from about 70 mph and up. I have yet to fix it but basically you just need to find a shop that can rebalance it for you. Shouldn't be too expensive and I hear the driveshaft isn't difficult to take off either. Hope that helps.

MakkMarci

iTrader: (1)

Yes, I found a shop, when they can rebalance my driveshaft.
We exchange my carrier.
I need rebalance my driveshaft, when exchange carrier?!? or gears?

MakkMarci

iTrader: (1)

sorry, my language is terrible
I hope you can understand me

elderon

Well if I'm understanding you. You shouldnt need to mess with the carrier or gears unless you are upgrading your gears. Just rebalance the driveshaft.